This invention relates generally to devices for interventional therapeutic treatment or vascular surgery for treatment of defects in the vasculature, and more particularly concerns a system and method for delivering an embolic coil to a treatment site in a vasculature of a patient, such as for treatment of aneurysms.
Aneurysms have been treated with external surgically placed clips, detachable vasoocclusive balloons and embolus generating vasoocclusive devices such as one or more vasoocclusive coils, which are typically either placed within a blood vessel to block the flow of blood through a vessel making up that portion of the vasculature through the formation of an embolus, or are placed within an aneurysm stemming from the vessel to form such an embolus within the aneurysm. Delivery of one or more of such vasoocclusive coils has typically been accomplished by pushing them through a catheter to the target site.
In one conventional technique, a conductive guidewire delivers a high frequency current through the guidewire to melt and sever a joint to detach an implanted device from the guidewire. The patient is grounded during the procedure, and current is introduced via the guidewire, rather than with a two way current path.
Another device is known in which a device to be implanted is detached by application of a high-frequency current which melts and severs a resin that is used to retain the device to be implanted until the device is to be deployed. In another known device, an electrolytically severable link is dissolved by activation of a power source electrically coupled to the electrolytically severable link to detach the device to be implanted.
An apparatus for deployment of a micro-coil is also known in which the micro-coil is detachably mounted to the distal portion of a pusher by a tubular collar that can be heated by an electrical resistance coil to expand the collar and release and deploy the therapeutic device.
Such devices that release the interventional device by melting or dissolving the intermediate section between the catheter tip and implanted device may cause thermal damage of surrounding tissues during detachment that can cause embolization in the bloodstream, and may also potentially release undesirable particles of materials into the bloodstream that can also cause embolization in the bloodstream.
In order to allow delivery and withdrawal of such embolic coils, one known implant delivery assembly utilizes a shape memory decoupling mechanism activated when exposed to body temperature. A cooling solution is flushed through the catheter during introduction and placement of the implant in order to prevent premature release of the implant prior to the time that the implant is to be released. Another implant delivery assembly includes an electrical heating system for heating the coupling mechanism to a temperature at which the shape memory material returns to its original shape, to deploy the implant.
A thermally activated occlusive implant delivery system is also known in which a pusher includes a distal coupling formed of shape memory material having different configurations dependent upon temperature, that interlocks with the implant in one configuration and that releases the implant in another configuration.
In another device for releasing an embolic coil inside an aneurysm, a coupling made of a shape memory alloy is responsive to a change in temperature beyond a predetermined transformation point so as to change the shape of the coupling from a first configuration, in which the coupling receives and holds the proximal end of the coil, to a second configuration in which the coil can be released from the coupling. An energy receiver is used to heat the coupling to a temperature above the transformation point with laser or electrical energy received from an external source.
There is a need for an improved apparatus for deploying therapeutic interventional devices with a strategically placed heating element that provides direct, even heating of a flexible shape memory polymer coupling releasably retaining an embolic coil for delivery when the heating element is energized, without causing thermal damage to surrounding tissues, and without releasing undesirable particles of materials into the bloodstream and risking the formation of emboli in the bloodstream. The present invention meets these and other needs.